updated README

Author: thinkswan

README.md

@@ -25,14 +25,32 @@ This will take the parents height, the elements own height and calculate the dis
 Options
 -------
 
-You can pass one parameter to the plugin, which is the css attribute that the value should be set on. The default is 'margin-top', but you can pass any attribute you would like. Most probably 'padding-top' or 'top'.
+You can pass 1 parameter and an options hash to the plugin.
+
+ - `onAttribute` - the css attribute that the value should be set on (default: `'margin-top'`)
+ - `verticalOffset` - the number of pixels to offset the vertical alignment by, ie. `10`, `"50px"`, `-100` (default: `0`)
+ - `parentSelector` - a selector representing the parent to vertically center this element within, ie. `".container"` (default: the element's immediate parent)
+
+Examples:
 
 	<script>
 	$(document).ready(function() {
 		$('#element-to-be-centered').flexVerticalCenter('padding-top');
 	});
 	</script>
 
+	<script>
+	$(document).ready(function() {
+		$('#element-to-be-centered').flexVerticalCenter('margin-top', { verticalOffset: 50 });
+	});
+	</script>
+
+	<script>
+	$(document).ready(function() {
+		$('#element-to-be-centered').flexVerticalCenter('padding-top', { verticalOffset: 50, parentSelector: '.parent' });
+	});
+	</script>
+
 
 Non-jQuery version
 ------------------